Software-Defined Networking (SDN) is a network organizing technique. An SDN with an OpenFlow protocol separates the data and control functions of networking devices, such as routers, packet switches, and LAN switches, by inserting a well-defined Application Programming Interface (API) between the two. In many large enterprise networks, routers and other network devices encompass both data and control functions, making it difficult to adjust the network infrastructure and operation to large-scale addition of enduser systems, virtual machines, and virtual networks.
In a hybrid SDN, engineers can run SDN technologies and standard switching protocols simultaneously on the physical hardware. A network manager can configure the SDN control plane to discover and control certain traffic flows while traditional, distributed networking protocols continue to direct the rest of the traffic on the network.
Under the hybrid network including SDN and legacy switches, when a network or network devices needs to be diagnosed, an SDN controller sends checking requests to the switches for network diagnosis. However, the network or the network devices can be heavily loaded by frequent checking when the sending of KeepAlive packets via the SDN controller is persistent, and errors cannot be immediately discovered.
In addition, the SDN controller needs extra packets, for example, pathChirp packets for checking of network state information, for example, bandwidth information. Therefore, the more switches being managed by the SDN controller, the more loadings the SDN controller will get.